Link Between Chest Pain Severity and MI Tenuous

Action Points

Explain that severity of chest pain in patients presenting to the emergency department is not an accurate indicator of the likelihood of myocardial infarction.

Point out that characteristics related to inhospital myocardial infarction included an elevated thrombolysis in myocardial infarction (TIMI) score, male sex, and arriving at the hospital via emergency medical services.

Severity of chest pain in patients presenting to the emergency department is not an accurate indicator of the likelihood of myocardial infarction, researchers suggested.

In a secondary analysis of a prospective cohort study, there was no association between patients' reporting severe chest pain on arrival at the hospital and their being given a diagnosis of acute myocardial infarction (RR 1.28, 95% CI 0.93 to 1.76), according to Meredith Edwards, BS, from Duke University Medical Center, and colleagues.

"We believe that it is common for lay people and attorneys to cite high pain score as an indication for a patient to remain in the hospital for further cardiac evaluation, yet our study demonstrates that this should not necessarily be the case," wrote Edwards and colleagues.

Only a small number of the six million emergency department visits each year relating to chest pain turn out to be myocardial infarctions.

However, in up to 5% of cases of myocardial infarction, patients are sent home inappropriately, according to researchers, which is a frequent cause of malpractice claims being filed against emergency physicians.

And in those claims, lawyers may question the judgment of a clinician's discharge decision if the patient reported a high pain score during evaluation, the researchers cautioned.

To answer the question of whether pain scores correlate with outcome in patients with suspected acute coronary syndrome, Edwards' group analyzed data collected during a study of risk stratification in the emergency department of the Hospital of the University of Pennsylvania in Philadelphia.

Their analysis included 3,306 patients whose mean age was 51.

Two-thirds were African Americans and 57% were women.

As part of their clinical evaluation, patients were asked to rate the severity of pain on a scale of 0 to 10, with a score of 9 or 10 being severe.

A total of 18% of patients reported severe pain.

While at the hospital, 105 patients were diagnosed with acute myocardial infarction based on troponin levels, 85 underwent percutaneous coronary intervention, 13 had coronary bypass artery grafting, and 16 died.

Within the subsequent month, another 18 patients died, 105 had a revascularization procedure, and six had myocardial infarctions.

Those who reported severe pain were no more likely to have an inhospital myocardial infarction than those with pain scores between 1 and 8 (3.9% versus 3.0%)

After adjusting for potential confounders, the researchers found that these factors related to inhospital myocardial infarction:

In the adjusted model, researchers found no correlation between acute myocardial infarction and pain severity (score 9 and 10), pain duration ( longer than an hour), age, or white race.

On the secondary outcome of 30-day cardiac events (composite of myocardial infarction, death, and revascularization), these factors were related:

Male sex, RR 1.53 (95% CI 1.16 to 2.01)

White race, RR 1.43 (95% CI 1.09 to 1.87)

Arrival by emergency medical services, RR 1.23 (95% CI 0.96 to 1.60)

High TIMI score, RR 2.24 (95% CI 1.39 to 3.60)

Again, there was no association with severe pain, pain lasting longer than an hour, or age.

The likely reason for the public and legal perceptions about severe pain may derive from traditional medical teachings that the pain associated with myocardial infarction is greater than that caused by other conditions such as angina, researchers said.

Nevertheless, researchers concluded, "[A]lthough pain management is an important issue to address clinically, pain severity itself should not be a factor in evaluating patients' risk for acute coronary syndrome in terms of discharge decisions."

The study was limited by being a secondary analysis, and there may have been confounding variables.

One potential confounder could have been whether or not patients had taken nitroglycerin before arrival at the hospital, although the researchers attempted to control for this by adjusting for transport by emergency medical services.

Another limitation was that patients were enrolled only during the 16 to 17 hours each day when research assistants were present in the emergency department, so patients seen at night were not included and may have differed from patients arriving during the day.

The researchers also noted that assessing for pain can be complex because of its subjectivity.

However, they explained that the numeric scale they used is widely used and easy to administer.

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